fn main() {
    let max_value: u128 = 0xf;
    for a in 0..=max_value {
        for b in 0..=max_value {
            let v = &(a..=b);
            for count in 1..=max_value*3 {
                assert!(count > 0);

                let niche = v.end().wrapping_add(1)..*v.start();
                let available = niche.end.wrapping_sub(niche.start) & max_value;

                let start = v.end().wrapping_add(1) & max_value;
                let end = v.end().wrapping_add(count) & max_value;
                let valid_range_contains = |x| {
                    if v.start() <= v.end() {
                        *v.start() <= x && x <= *v.end()
                    } else {
                        *v.start() <= x || x <= *v.end()
                    }
                };
                if (count > max_value || valid_range_contains(end)) != (count > available) {
                    dbg!(v, count);
                    panic!();
                }
            }
        }
    }
}